Continuous synthetic fibers, or filaments, such as have been used in the textile industry have commonly been produced in one of two different ways. In one way a normally viscous material, such as a modified cellulose, for example, is forced through a spinneret and the emerging discrete streams are chemically treated to congeal the material and thereby form it into continuous filaments. In the other way, a thermoplastic resin is liquified, as by melting or dissolving it in an appropriate solvent, and forcing it through a conventional hole spinneret, and the emerging discrete streams congeal on cooling to form filaments. The latter method also has been used to form continuous filaments of glass adapted for various uses.
There are several disadvantages inherent in these methods. Production rates are limited, and the fine openings in the spinneret have a tendency to clog or plug up with material, thereby requiring either a new spinneret or a great deal of effort to correct the situation. It is also very difficult to make discontinuous, or short, fibers with any high degree of uniformity.
Inorganic "wools" for uses as heat insulation have been produced by treating a stream of molten slag, glass, or the like with a high-velocity stream of air, stream, or gas which shatters the molten material into fine fibers. Fibers so produced lack uniformity and frequently are characterized by beaded ends rendering them unsuitable for certain uses. Glass wool has also been produced by feeding a glass rod at right angle to the axis of and into a high velocity, turbulent gas flame which both melts the glass and shatters the melt into fibers. Fibers produced in these ways have wide variations in size and lengths and as a result of turbulence existing in such equipment, are rough, creped and weak.
It has further been proposed to create continuous fibers or filaments by drawing them under tension from points on the uninterrupted surface of molten baths of glass. Such a method is disclosed in U.S. Pat. No. 2,235,352 to Bates. According to the Bates disclosure, the locations on the bath surface from which the fibers are drawn are determined initially by use of a horizontally extending element the upper edge of which is serrated in effect. This element is first immersed in the bath to submerge the serrations and then raised to bring the serrations above the glass level. Once the drawing of filaments from the serrations has started, the serrated element is lowered beneath the bath surface and tension in the filaments continues to draw them from the bath. One drawback to this method is that the size and length of the fibers cannot be closely controlled, as they are formed from an excess pool of material, not a metered feed.
It is, therefore, an object of this invention to provide a process by which liquid congealable materials can be formed into fibers with a high degree of uniformity in length and cross-section and under conditions capable of control with precision and of providing high production rates.